Structural insights into assembly, operation and inhibition of a type I restriction-modification system
Structural insights into assembly, operation and inhibition of a type I restriction-modification system
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I 型限制修饰系统的组装、操作和抑制的结构见解
DOI：
10.1038/s41564-020-0731-z
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发表时间：
2020-06-01
影响因子：
28.3
通讯作者：
Gao, Pu
中科院分区：
文献类型：
--
作者：
Gao, Yina;Cao, Duanfang;Gao, Pu
这项研究为了解I型限制性内切酶修饰系统的结构、组装和动力学以及噬菌体蛋白对其抑制作用提供了新的见解。I型限制性内切酶修饰(R-M)系统广泛存在于原核生物基因组中，对外来DNA具有强大的保护作用。它们是具有甲基转移酶、核酸内切酶和转位酶活性的多亚单位酶。尽管在过去的50年里进行了广泛的研究，但人们对这些复杂机器的分子机制知之甚少。在这里，我们报道了具有代表性的EcoR124I R-M系统在不同组件(R2M2S1、R1M2S1和M2S1)中与靶DNA以及噬菌体和可移动遗传元件编码的反限制蛋白OCR和ARDA结合的冷冻电子显微镜结构。EcoR124I可以通过不同的构象精确地调节不同的酶活性。EcoR124I的显著构象转变依赖于在单个亚基和组装复合体水平上的内在灵活性。此外，OCR和ARDA使用DNA模拟策略来抑制多种活性，但不会阻止络合物的构象转变。这些结构发现，加上对关键分子间接触的突变研究，为了解I型R-M系统的组装、操作和抑制机制提供了见解。
This study provides new insights into the structure, assembly and dynamics of type I restriction-modification systems, and their inhibition by phage proteins.Type I restriction-modification (R-M) systems are widespread in prokaryotic genomes and provide robust protection against foreign DNA. They are multisubunit enzymes with methyltransferase, endonuclease and translocase activities. Despite extensive studies over the past five decades, little is known about the molecular mechanisms of these sophisticated machines. Here, we report the cryo-electron microscopy structures of the representative EcoR124I R-M system in different assemblies (R2M2S1, R1M2S1 and M2S1) bound to target DNA and the phage and mobile genetic element-encoded anti-restriction proteins Ocr and ArdA. EcoR124I can precisely regulate different enzymatic activities by adopting distinct conformations. The marked conformational transitions of EcoR124I are dependent on the intrinsic flexibility at both the individual-subunit and assembled-complex levels. Moreover, Ocr and ArdA use a DNA-mimicry strategy to inhibit multiple activities, but do not block the conformational transitions of the complexes. These structural findings, complemented by mutational studies of key intermolecular contacts, provide insights into assembly, operation and inhibition mechanisms of type I R-M systems.